To determine the position of a control element, such as a throttle valve, which is exposed to high temperatures, there are used in known manner mechanical potentiometers which are mechanically connected to the control element. Analog signals are output to an A/D converter and then to an evaluation unit.
A disadvantage of such devices, however, is that the mechanical potentiometers undergo considerable wear, whereby additional interfering variables falsify the measured result.
German Patent Application DE 3345804 A1 discloses an instrument for contactless electronic measurement of the angle of a mechanical actuator. In this instrument a shaft, connected mechanically to the actuator protrudes form the instrument and a rotatable magnet is attached to the shaft. A sensor element is disposed in the casing opposite the rotatable magnet. A Hall element cannot be utilized under these conditions, since the instrument is exposed to relatively high temperatures and thereby output signals of the Hall element drift very greatly. Therefore a flux gate principle and not the Hall effect is used for this purpose.
Various contactless devices containing Hall generators using the Hall effect for measuring lengths and/or angles are disclosed in German Patent Application DE 4405513 A1, German Patent DE 4408056 C2 and German Patent Application DE 1970987 A1. These measuring devices are also imprecise as regards their measured results at relatively high temperatures, since here also the influence of temperature on the magnet and its flux density is not precluded.